U.S. patent number 4,642,652 [Application Number 06/664,043] was granted by the patent office on 1987-02-10 for unfoldable antenna reflector.
This patent grant is currently assigned to Messerschmitt-Boelkow-Blohm Gesellschaft mit beschraenkter Haftung. Invention is credited to Franz Drachenberg, Horst Heinze, Henning Herbig, Knud Pontoppidan.
United States Patent |
4,642,652 |
Herbig , et al. |
February 10, 1987 |
Unfoldable antenna reflector
Abstract
An umbrella type unfoldable antenna reflector net is supported
by carrier bs extending radially from a carrier body and by
auxiliary ribs extending between adjacent carrier ribs. Bracing
wires are connected between the carrier ribs and the auxiliary
ribs. The tension of the bracing wires, which in the unfolded state
of the reflector net extend substantially in the direction of
chords, is adjustable by respective adjustment members so that the
bracing tension force has a force component which extends
substantially perpendicularly to a plane defined by the unfolded
reflector net. The adjustment members permit adjusting the
reflector net into a parabolic shape.
Inventors: |
Herbig; Henning (Holzkirchen,
DE), Heinze; Horst (Westerham, DE),
Drachenberg; Franz (Baldham, DE), Pontoppidan;
Knud (Copenhagen, DK) |
Assignee: |
Messerschmitt-Boelkow-Blohm
Gesellschaft mit beschraenkter Haftung (Munich,
DE)
|
Family
ID: |
6212831 |
Appl.
No.: |
06/664,043 |
Filed: |
October 23, 1984 |
Foreign Application Priority Data
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|
|
|
Oct 27, 1983 [DE] |
|
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3338937 |
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Current U.S.
Class: |
343/915 |
Current CPC
Class: |
H01Q
15/161 (20130101) |
Current International
Class: |
H01Q
15/14 (20060101); H01Q 15/16 (20060101); H01Q
015/20 () |
Field of
Search: |
;343/912-915,840,DIG.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Microwaves, Mar. 1974, p. 14..
|
Primary Examiner: Lieberman; Eli
Attorney, Agent or Firm: Fasse; W. G. Kane, Jr.; D. H.
Claims
What is claimed is:
1. An unfoldable antenna reflector for a metallic antenna reflector
net, comprising a central carrier body, a plurality of carrier ribs
for carrying said reflector net, support means for pivotally
securing one end of said carrier ribs to said carrier body so that
said carrier ribs are movable between an open substantially
radially extending position and a closed substantially axially
extending position, a plurality of auxiliary ribs disconnected from
said central carrier body and secured to said reflector net, said
auxiliary ribs being located so that one or more auxiliary ribs are
positioned between adjacent carrier ribs, flexible bracing wires
for connecting said auxiliary ribs to said carrier ribs, securing
means for operatively connecting one end of each bracing wire to an
adjacent carrier rib, adjustable anchoring means operatively
securing a respective auxiliary rib to the respective opposite end
of a corresponding bracing wire, said bracing wires extending, in
the unfolded state of said reflector net, in the direction of a
resultant bracing tension force having two bracing tension force
components one of which extends substantially perpendicularly to a
plane defined by said reflector net in its unfolded state.
2. The antenna reflector of claim 1, wherein a plurality of said
adjustable anchoring means are distributed along the length of the
respective auxiliary ribs.
3. The antenna reflector of claim 1, wherein each of said
adjustable anchoring means comprise an adjustable member (7) to
which the respective bracing wire is operatively secured, and a
fixed member (6) holding said adjustable member in an adjustable
manner, said fixed member (6) being secured to the respective
auxiliary rib, said adjustable member being movable substantially
perpendicularly to said plane defined by said reflector net.
4. The antenna reflector of claim 3, wherein said adjustable member
is a sleeve (7) slidably received in said fixed member in the form
of a hollow tube (9), said adjustable anchoring means further
comprising a threaded spindle (8), means rotatably securing said
threaded spindle to said auxiliary rib (4), and a threaded nut
rigidly secured to said sleeve (7), said threaded spindle (8) being
received in said threaded nut for adjusting the position of said
sleeve and thus the tension of the respective bracing wires
operatively secured to said sleeve.
5. The antenna reflector of claim 4, wherein said securing means
for said threaded spindle comprise a disk (10) secured to said
respective auxiliary rib and a socket in said disk in which one end
of said threaded spindle is rotatably held for said adjusting.
6. The antenna reflector of claim 1, further comprising holding
bails (11) secured to said auxiliary ribs (4) and releasable
connecting means for releasably securing said holding bails to said
carrier ribs for holding said reflector net in a folded condition,
said releasable connecting means being removable prior to unfolding
said reflector net.
7. The antenna reflector of claim 1, wherein said carrier ribs
comprise hinging means operatively interposed intermediate the ends
of said carrier ribs for folding each carrier rib back upon itself,
and wherein said auxiliary ribs comprise elastically flexible
hinging zones in such positions intermediate the ends of said
auxiliary ribs that the auxiliary ribs are also foldable together
with the carrier ribs.
8. The antenna reflector of claim 1, wherein said auxiliary ribs
are made of fiber composite material.
9. The antenna reflector of claim 8, wherein said composite
material comprises aramide fibers.
10. The antenna reflector of claim 8, wherein said fiber composite
material comprises carbon fibers.
11. The antenna reflector of claim 8, wherein said auxiliary ribs
of fiber composite material comprise along their length elastically
flexible hinging zones formed of fiber material without any
embedding resin in said hinging zones, said hinging zones
permitting folding said auxiliary ribs.
Description
FIELD OF THE INVENTION
The invention relates to an unfoldable antenna reflector,
especially a metallic net reflector provided with a number of
carrier ribs, especially rigid carrier ribs operatively secured to
a carrier body in a pivoting or journalling manner so that the
carrier ribs may be tilted outwardly during the unfolding to extend
substantially radially upon completion of the unfolding operation.
These carrier ribs support the metallic reflector net.
DESCRIPTION OF THE PRIOR ART
A net reflector for such an antenna as mentioned above is primarily
used in satellites. An antenna of this type is shown in
"Microwaves" Mar. 1974, page 14. This known net reflector comprises
in addition to the reflector net proper a further adjusting net.
The reflector net proper is secured to the upper side of the
pivotable carrier ribs while the adjusting net is attached to the
back side of the carrier ribs. The adjusting net is connected to
the reflector net in the sectors between the radially outwardly
pivoted carrier ribs by a substantial, large number of adjustable
tensioning or bracing wires. It is the purpose of these adjustable
bracing wires to make sure that the reflector net assumes in its
unfolded state the desired parabolic shape as precisely as
possible, even in the sectors between the carrier ribs which
determine said parabolic shape. However, the adjustment of the
large number of tensioning wires requires a substantial work
effort, especially also because the adjustment of one wire has an
effect on the neighboring or adjacent adjustment points so that
repeated readjustments are necessary. These difficulties can be
reduced as the number of carrier ribs employed is increased,
whereby these carrier ribs must be of rigid construction to provide
a defined parabolic shape.
OBJECTS OF THE INVENTION
In view of the above it is the aim of the invention to achieve the
following objects singly or in combination:
to construct an unfoldable antenna netting reflector of the type
mentioned above in such a manner that the effort and expenditure
for the adjustment of the desired parabolic shape of the reflector
net is optimally reduced;
to provide a support structure for the antenna reflector net which
itself already causes the reflector net to assume a uniform
curvature substantially approximating the desired parabolic
shape;
to employ auxiliary ribs which help in causing the reflector net to
assume the desired uniform curvature while at the same time
permitting reducing the number of the relatively heavy carrier
ribs;
to increase the total number of ribs used to thereby also improve
the radiation characteristics of the antenna reflector; and
to substantially reduce the influence of temperature changes on the
shape and radiation characteristics of the antenna reflector.
SUMMARY OF THE INVENTION
According to the invention the above mentioned antenna reflector
comprises one or several auxiliary ribs secured to the reflector
net and located radially between the adjacent carrier ribs. These
auxiliary ribs are secured to the adjacent carrier ribs by means of
adjustable bracing or tensioning wires. These adjustable bracing
wires may be so tensioned that the bracing wires have a force
component which extends substantially perpendicularly relative to
the plane which is defined by the reflector net in its unfolded
condition. Stated differently, the bracing or tensioning wires
extend along a force resultant, the components of which extend
substantially perpendicularly to the plane of the reflector net and
substantially in parallel thereto. The auxiliary ribs, which are
attached to the reflector net in the sectors between the carrier
ribs, make sure that the reflector net assumes at least in the
zones of these auxiliary ribs a continuous or uniform curvature
right from the start when the net reflector is unfolded. This
initial shaping of the reflector net by the auxiliary ribs is due
to the fact that a point to point adjustment with the aid of
individual tensioning wires which in the prior art used to cause
depressions in the reflector net, has been avoided according to the
invention.
According to the invention it is possible to use a substantially
smaller number of bracing wires between the auxiliary ribs and the
carrier ribs than has been possible heretofore in the conventional
construction of a reflector with a reflecting net proper and an
adjusting net. The lower number of bracing or tensioning wires is
possible according to the invention due to the cross component or
rather, due to the force component extending perpendicularly to the
plane defined by the reflector net because such force component is
capable to apply a rearwardly directed tension to the auxiliary
ribs, whereby such tension achieves a good approximation of the
shape of the auxiliary ribs to the desired parabolic form. Further,
additional adjusting points are not necessary between the auxiliary
ribs and the carrier ribs, nor are such points necessary between
the auxiliary ribs themselves. Accordingly, it is possible to
substantially reduce the entire investment heretofore required for
the ajustment effort. Yet another advantage is seen in that the
number of the relatively heavy carrier ribs has been reduced which
has an advantageous effect on the overall weight of satellites
carrying such antennas. On the other hand, the total number of ribs
used can be increased by using the auxiliary ribs which has the
added advantage that the radiation characteristics of the antenna
have been improved. For example, the position and number of the
side lobes of the antenna characteristic which occur in addition to
the main lobe in the antenna characteristic or radiation diagram
depends on how many ribs are used altogether. The more
parabolically shaped ribs are used in the antenna reflector, the
further outwardly will the side lobes be shifted. Thus, the antenna
net reflector according to the invention constitutes a simple and
economical concept which is advantageously usable in many
instances.
Another advantage of the invention is seen in that the temperature
changes to which the present antenna may be exposed have a smaller
influence on the antenna characteristic because the bracing wires
are now secured to the carrier ribs which are relatively stable in
a thermal sense. Heretofore, temperature changes were effective on
the adjusting net which was thus exposed to thermally caused
contractions and/or expansions, whereby the adjusting precision was
impaired. The invention has avoided this problem. Yet another
advantage of the adjustment according to the invention is seen in
that a displacement of any adjustment point has a much smaller
cross effect on any of the neighboring adjustment points than was
the case heretofore in an antenna comprising the above mentioned
conventional double net concept.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly understood, it will now
be described, by way of example, with reference to the accompanying
drawings, wherein:
FIG. 1a is a plan view in the direction of the central axis of the
antenna reflector and into the open reflector, whereby the central
axis extends perpendicularly to the plane of the drawing;
FIG. 1b is a sectional view substantially along section line 1b--1b
in FIG. 1a;
FIG. 2a is a sectional view substantially along section line 2a--2a
in FIG. 1a, whereby a single auxiliary rib is located between two
adjacent carrier ribs;
FIG. 2b is a sectional view substantially similar to that of FIG.
2a, however, showing two auxiliary ribs located between two carrier
ribs;
FIG. 2c is a sectional view similar to that of FIGS. 2a or 2b, but
showing three auxiliary ribs between two carrier ribs;
FIG. 3 is a sectional view on an enlarged scale through an
adjustable anchoring device for connecting the bracing wires to an
auxiliary rib;
FIG. 4 shows a portion of a folded antenna reflector according to
the invention substantially in the direction of the section plane
2a--2a in FIG. 1, wherein the auxiliary ribs are anchored to the
carrier ribs by holding bails which are releasable when the antenna
is to be unfolded;
FIG. 5 is a view substantially in the same direction as defined by
the section plane 1b--1b in FIG. 1a, however showing modified
carrier ribs which are foldable back upon themselves; and
FIG. 6 shows on an enlarged scale an auxiliary rib for use in the
embodiment of FIG. 5, whereby such auxiliary rib is provided with a
hinging zone so that the auxiliary rib may also be folded back upon
itself .
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE
BEST MODE OF THE INVENTION
FIG. 1a shows an antenna reflector according to the invention in
its unfolded condition comprising, for example, a total of twelve
carrier ribs 3 and twelve auxiliary ribs 4 located in the sectors
between adjacent carrier ribs. The radially inner ends are
pivotally secured by journals or hinges 3' to a carrier body or hub
1 as shown in FIG. 1b, whereby the carrier ribs 3 may be folded
into the folded state as shown by dash-dotted lines in FIG. 1b. The
carrier ribs 3 are equipped with spacer elements 16 shown in FIG.
1b to which the reflector net 2 is secured to assume a parabolic
shape. The spacer members increase in size radially outwardly so
that the shape of the net 2 assumes the form of a rotational
paraboloid as closely as possible. Preferably, the spacer elements
16 are adjustable.
The net 2 is made of metal wire or metallized threads such as
synthetic material forming a net type webbing. The mesh size of the
net or webbing is selected with due regard to the wavelength to be
radiated by the antenna.
The material for making the carrier ribs 3 should be so selected
that these ribs 3 have a high stiffness of their own while
simultaneously being as lightweight as possible. It has been found
that fiber reinforced synthetic materials are well suitable for the
present purposes.
The auxiliary ribs 4 are not secured to the hub 1, rather, the
auxiliary ribs 4 are secured to the reflector net 2, preferably to
the upper side thereof, whereby these ribs may be glued or sewn to
the reflector net. Tensioning or bracing wires 5 are secured to the
auxiliary ribs 4 at one end of the wires by adjustable anchoring
means 6 to be described in more detail below with reference to FIG.
3. The other end of the tensioning or bracing wires 5 is connected
to the carrier rib as shown at 5' in FIG. 2a. The wires 5 and the
adjustable anchoring means 6 are located behind the antenna
reflector net 2. The anchoring means 6 are accessible from the
backside of the reflector net for their adjustment in order to
bring the auxiliary ribs into the desired parabolic shape. For this
purpose the auxiliary ribs 4 have a certain flexibility. However,
it is possible to preshape the auxiliary ribs 4 so that they have
an inherent stiffness conforming to the parabolic shape, whereby
said adjusting means may not be necessary at all or substantially
simpler adjusting means could be employed.
FIG. 2a shows two carrier ribs 3 and a single auxiliary rib 4
arranged centrally between the two carrier ribs with only a pair
bracing wires 5 interconnecting the carrier ribs 3 with the
auxiliary rib 4. The carrier ribs 4 are, for example, cut from
tubular stock having, again as an example, a rectangular
cross-sectional shape. The net 2 is secured to the carrier rib 3 by
the above mentioned spacer members 16 which shape the net 2 into
the desired parabolic form at least in a first approximation which
is then improved upon by the adjustment of the wires 5 and thus of
the curvature of the auxiliary ribs 4. Suitably, the auxiliary ribs
4 are attached to the outwardly facing surface of the reflector net
2. The above mentioned anchoring means 6 are secured to the
backside, whereby the wires 5 are so oriented that they extend in
the direction of a resultant R indicated by an arrow head in one of
the wires 5 in FIG. 2a. The resultant R has two force components A
and B which are so oriented that the cross component A extends
substantially perpendicularly to a plane defined by the net 2 while
the component B extends substantially in parallel to the plane
defined by the net 2. The direction of these force components A and
B is such that the pull required for the adjustment of the
auxiliary ribs 4 in the downward direction, that is rearwardly of
the net 2, is provided. It has been found that fibers of quartz are
suitable for making the bracing or tensioning wires 5.
FIG. 3 shows one possible example embodiment of an adjustable
anchoring means 6 as used in FIGS. 2a, 2b, and 2c for connecting
the wires 5 to the auxiliary rib 4 in FIG. 2a and the wires 5a and
5b to the auxiliary ribs 4' in FIG. 2b, and the wires 5a, 5b, 5c to
the auxiliary ribs 4" in FIG. 2c.
In the sectional view of FIG. 3 the anchoring means or device 6 is
secured to the auxiliary rib 4 which in turn is secured to the net
2. The rib rests on the top surface of the net 2 and extends
substantially perpendicularly to the plane of the drawing.
A plurality of adjustable anchoring devices are distributed along
the length of each of the auxiliary ribs 4. Each of these
adjustable anchoring devices 6 comprises an adjustable member 7,
for example in the form of a hollow tubular sleeve 7 having a free
outer end to which the bracing wires 5 are operatively connected as
shown at 7'. The adjustable sleeve 7 is slidingly received in an
adjustable manner in a fixed member 9 such as a hollow tubular
member which in turn is secured to the respective auxiliary rib 4
so that the sleeve 7 is slidable up and down in the sleeve 9. The
upper end of the sleeve 9 is rigidly secured to a socket 10' which
in turn is part of or secured to a disc 10. The disc 10 rests
against the bottom side of the antenna net 2 and is secured to the
rib 4, for example, by rivets 17 which also hold a counter washer
17' resting against the upper or facing side of the net 2. The
socket 10' extends through the net 2, through the rib 4, and
through the counter washer 17'.
The adjustable sleeve 7 has in its sides two longitudinal guide
grooves 18 extending in parallel to the longitudinal axis of the
guide sleeve 7 and cooperating with two cams 19 at the inner upper
end of the tubular member 9. The cams 19 engage in the grooves 18,
thereby preventing the rotation of the sleeve 7 while
simultaneously guiding the axial up and down movement of the sleeve
7 under the control of a threaded spindle 8 having a head 21
received in the socket 10' and rotatably held by a spring ring or
locking washer 22. The outer free end of the adjustable slide
sleeve 7 is provided with a threaded nut 20 in which the threaded
spindle 8 is received. The threading of the spindle 8 and of the
nut 20 is preferably of the self-locking kind. Except for a small
play as permitted by the position of the locking washer 22, the
spindle 8 is not axially movable. However, rotation of the spindle
8, for example, by inserting a tool into a respectively shaped
recess 8' in the head 21 of the spindle 8, the sleeve 7 is axially
adjustable up and down, whereby the wires 5 are tensioned. Such
tensioning of the wires 5 in turn is transmitted to the reflector
net 2 and to the respective auxiliary rib 4, whereby these ribs are
pulled more or less into the down direction where the adjustment
devices 6 are located. The adjustment direction of the net 2 and
the rib 4 is indicated by the arrow A in FIG. 2a.
FIG. 4 illustrates in a stylized manner a sectional view through
three carrier ribs 3 in the folded state of the antenna in which
the also folded reflector net 2 is forming the meandering shape
between adjacent spacer members 16 secured to the ribs 3 and the
auxiliary ribs 4. The anchoring devices 6 are rigidly secured to
the spacer members 16 by holding bails 11 which are attached by
releasable screws or clamps 11' to the spacers 16 in the folded
condition. When the antenna is to be unfolded, the screws or clamps
11' are first released. On the other hand, when the antenna is to
be folded and held in the folded condition the screws or clamps 11'
are again tightened. In this manner it is possible to positively
keep the antenna in the folded state during the starting and
transporting phase of a satellite, for example. This feature of the
invention has the advantage that the auxiliary ribs 4 and the
adjustable anchoring means 6 assume a defined position during times
when the antenna is exposed to vibrations and substantial loads.
Thus, these screws or clamps 11' together with the bails 11 make
sure that the adjustable anchoring devices 6 do not become
entangled with the reflector net when the net is folded. The
reflector net 2 is only free to fold in the relatively narrow areas
between the ribs 4 and the adjacent spacer members 16. This feature
of holding the net 2 in a relatively well defined position even in
the folded state has the advantage that the net 2 is exposed during
the starting phase only to the loads of its own mass. Contrary to
this advantage, in a reflector having two nets, namely, the
reflector net and the adjustment net, the reflector net is exposed
during the starting accelerations to the load caused by the mass of
the adjustment net and to the load caused by the mass of the
tensioning wires and their respective adjustment elements. The
invention avoids this loading of the net 2 during the starting
phase because the bails 11 take up such loads as long as the net 2
is still in the folded state which is the case during starting of a
satellite launching rocket.
FIG. 5 illustrates carrier ribs 13 which function in the same
manner as the carrier ribs 3. However, each carrier rib 13 has at
least two, or even more sections 13' and 13" which are joined to
each other by hinge means 30. As in FIG. 1b, the lower ends of the
rib sections 13' are hinged to the hub 1 by hinges 31. Here again,
the spacer members 16 are so positioned that their free ends define
a parabolic curve against which the net 2 may rest. If desired,
each individual spacer member 16 may be adjustable as is seen in
FIG. 4 wherein a threaded stem of the spacer member reaches into a
threaded hole of a socket secured to the respective rib 3. The
auxiliary ribs 4 are not shown in FIG. 5 because they are located
above and below the plane of the drawing. However, it will be
appreciated that the auxiliary ribs 4 in FIG. 5 will also have a
foldable joint at the locations 23. The net itself is sufficiently
flexible for such folding.
As shown in FIG. 6 the auxiliary ribs 4 may comprise rods 14 of
fiber composite material provided with hinging zones 12 which will
be located at the locations 23 in FIG. 5. These hinging zones 12
may, for example, comprise only the fibers 15 without the addition
of the synthetic resin matrix material which is provided in the
rods 14 outside the fibers 15 of the hinging zone 12.
Although the invention has been described with reference to
specific example embodiments, it will be appreciated, that it is
intended to cover all modifications and equivalents within the
scope of the appended claims.
* * * * *